In modern life, there are increasing applications for wireless network. For example, display devices, such as projection devices, can be connected with computers, mobile phones and other terminals over the wireless network, so that videos, images and other contents in the terminals can be viewed on the display devices. While wireless work provides convenience, issues of the security between display devices and terminals need to be considered. Because wireless electromagnetic waves spread in all directions in the wireless transmission process, a third party may interrupt or intercept transmit content. Therefore, secure transmission methods need to be provided.
In prior art, a partnership between display devices and terminals can be established by negotiating a shared key. For example, random number, as a shared key, is displayed on the projection device, then users manually enter the shared key to a terminal, or the shared key is transmitted from the projection device to the terminal over the wireless network. Finally, the shared key is used to encrypt the transmission content, and the encrypted content is transmitted from the terminal to the projection device.
In the above-mentioned process, inventor found that the prior art has at least the following problems:
The method for manually entering the shared key is neither convenient nor secure, while the method for transmitting the shared key over the wireless network also makes the shared key exposed to an unsafe environment.